Device and method for parallel powering

ABSTRACT

The invention relates to powering one or more devices, in particular in the context of Power-over-Ethernet (PoE). In an embodiment of the invention, it is proposed to equip each node ( 11 ) with a PD interface ( 22 ) that can signal multiples of the standard defined unity load (25 kΩ with tolerances) during the detection process and increase the load during a sequence of detection attempts. In that way, several nodes ( 11 ) can share one PSE outlet and determine the number of neighboring loads ( 11 ). At the same time, each node ( 11 ) will offer full functionality during “normal” stand-alone wiring. This powering concept can be combined with full or limited data communication capabilities.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is the U.S. National Phase application under 35 U.S.C.§ 371 of International Application No. PCT/EP2016/053435, filed on Feb.18, 2016, which claims the benefit of European Patent Application No.15156887.0, filed on Feb. 27, 2015. These applications are herebyincorporated by reference herein.

FIELD OF THE INVENTION

The present invention is related to powering one or more devices, inparticular in the context of Power-over-Ethernet (PoE). The invention isin particular related to PoE lighting systems.

BACKGROUND OF THE INVENTION

According to the original concept of Power-over-Ethernet (PoE, see, forexample, IEEE 802.3 af/at standard), every PoE device or powered device(PD) (e.g. luminaires, sensors etc.) has its own connection to the powersourcing equipment (PSE), because the power is distributed in a starlike cabling structure, potentially increasing the total cable length.

In many installations cabling loads in a chain would be interesting,such that a part of the cable is shared by several loads. The individualnodes in a chain may even leverage from information on the number ofloads in this PSE segment, e.g. in order to prevent overloading the PSE.

Upcoming solutions with a low voltage DC distribution e.g. following thePoE standard are hampered as infrastructure changes need to be donebefore new lighting devices can be mounted. Other DC distributionsystems as used in lighting not adhering a PoE standard commonly havethe same high investment in infrastructural change and smallinstallations do mostly not make any commercial sense.

A typical PoE lighting system is illustrated in FIG. 1 with a PSE 1 anda number of PDs 2 in the form of luminaires. Each luminaire 2 isconnected by a dedicated cable 3 to the PSE 1, which is provided with amains connection 4 and an Ethernet connection 5. A typical luminaire 2for such system comprises LED modules generating light and an electronicsection controlling the LED current as well as interfacing to the PoEconnection for negotiation and voltage adaptation.

US 2010/0217447 A1 is related to a detection of multiple powered devicesconnected to an inline power delivery channel. It is disclosed toprovide multiple PDs (number n) such they each provide a resistance ofn·25 kΩ, so that the parallel combination equals the standard 25 kΩ andis correctly detectable by the PSE. US 2010/0217447 A1, however, doesnot disclose how the number of PDs is determined in the first place andhow the resistance provided by the PD (i.e. the multiple of 25 kΩ) isset.

US 2011/0885584 A1 is related to a long-reach Ethernet system and relay.A case is discussed where a number of relays and an Ethernet terminalare connected in parallel to form a powered load. In order to decreasean influence of the relays on the PD in-position detection, thein-position indication resistance of the relays is made much larger than26.5 kΩ (>265 kΩ, e.g. 470 kΩ), such that the parallel in-positionindication equivalent resistances of the relays and the PD are basicallythe same as the PD in the first place. It may be said that, according toUS 2011/0885584 A1, the relays are made “invisible” in the parallelconnection for detection by the PSE. However, due to the change in thein-position indication, the relays may not be connected to the PSE alone(or would at least not be detected as potential PDs).

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for a parallelconnection or coupling for PDs to a common supply line, while the PDs onthe one side may still properly comply with, for example, the PoErequirements even if connected alone and while further there isflexibility and ease of use in regard to the number of parallel PDsprovided.

In a first aspect of the present invention a device allowing parallelpowering is presented, comprising characteristic setting unit forsetting a characteristic, wherein the characteristic is used forsignaling the presence of a powered device and wherein thecharacteristic is to be detected by a power source equipment via asupply line for powering, a sensor coupled to the supply line, whereinthe sensor is arranged for checking for an application of a detectionvoltage and/or detection current by the power source equipment to thesupply line and for outputting a sensor signal, and a controller coupledto the characteristic setting unit and the sensor, wherein thecontroller is arranged, upon receipt of the sensor signal from thesensor indicating the application (of the detection voltage and/ordetection current by the power source equipment to the supply line) inabsence of a coupling with the power source equipment (i.e. the powersource equipment providing operational power), for controlling thecharacteristic setting unit so to change the characteristic.

In a further aspect of the present invention, a method of parallelpowering powered devices via a supply line is presented, comprising oneor more repetitions of the steps of setting a characteristic used forsignaling the presence of a powered device, wherein the characteristicis to be detected by a power source equipment via the supply line,checking for an application of a detection voltage and/or detectioncurrent by the power source equipment to the supply line, and causing achange of the setting of the characteristic in case the checkingindicates the application of the detection voltage and/or detectioncurrent when the powered device is not coupled with the power sourceequipment.

It is to be noted that the term “powered device” is not to be understoodas implying that the power provided to the powered device is alsoconsumed partially or completely by the powered device, as the providedpower may as well be forwarded to a different entity. In other words, ina situation where, for example, a conventional Power-over-Ethernetdevice is combined with a separate unit, the separate unit including thecharacteristic setting unit (in this case in the form of an interface,see below), the sensor and the controller as defined in claim 1, theseparate unit alone is already to be considered as a “powered device”,regardless of the power being consumed by the conventional device.Nevertheless, any combination of such separate unit and conventionaldevice is still a “powered device”, as long as the defined units areprovided in either one of separate unit and device.

The invention is based on the following considerations, which will beexplained while referring to Power-over-Ethernet as an example of acontext for powering devices. In order to be recognizable according tothe PoE standard, the combined load (i.e. the combination of powereddevices provided in parallel on the supply line) has to present animpedance value (the characteristic to be presented in case ofPower-over-Ethernet) as prescribed by the PoE-standard (in case of onlyconsidering resistance as value between 23.75 kΩ and 26.25 kΩ, typically25 kΩ). If the impedance seen by the PSE does not fall into theprescribed range, the PSE will not continue to the classification andthe provision of power, as the impedance check is performed as asafeguard against damaging devices not compliant with the PoE standard.In case no knowledge is (surely) provided on the side of the powereddevices as to how many other powered devices are connected in parallelto the supply line (e.g. the Ethernet cable), a successful detection bythe PSE may nevertheless be achieved in case the powered devices followa consistent approach along the line of trial and error. If a resistanceof 25 kΩ multiplied by the (unknown) number of parallel devices ispresented by each of the device, the combined resistance (due to theparallel arrangement) becomes 25 kΩ. Thus, the present inventionprovides for a change in the impedance value in case an unsuccessfulattempt for a detection of compliant devices is recognized. If alldevices connected in parallel follow this approach, eventually thecorrect multiplier may be found. Preferably, the change is done in apredetermined and synchronized manner, so that the number of attemptsuntil success may be kept low, even though a random change (withinlimits) or different sequences with changing offsets may be used.

In an advantageous embodiment, the device is a powered device (in thebroadest sense as discussed above, even though this also applies to apowered device per se) arranged for being powered via the supply lineand the characteristic setting unit is an interface for presenting thecharacteristic to the supply line in order to signal the presence of thepowered device.

A powered device according to this embodiment differs from conventionalpowered devices (which are arranged only for presenting one singlepredetermined characteristic, e.g. a fixed resistance of 25 kΩ asdiscussed above) in particular in the possibility of presentingmodifying characteristics, so that being taking into account the alsomodified characteristics presented by parallel powered device, thecombined characteristic detected by the power source equipment allowsfor a successful coupling.

In a further advantageous embodiment, the device is a connecting unitarranged for coupling the power source equipment and at least onepowered device and wherein the device includes at least a portion of thesupply line.

In contrast to the above case, where the characteristic presented by thepowered device to the supply line is changed, in this embodiment, thecharacteristic presented by the powered device(s) to be powered inparallel (which might as well be conventional powered devices) mayremain unchanged, while the characteristic detected by the power sourceequipment is modified by the characteristic setting unit, e.g. by addingan additional characteristic. Let us assume, for simplicity, a casewhere two conventional powered device (each having an internalresistance of 25 kΩ) are to be connected in parallel to a single port ofa power source equipment. In case such conventional powered device wouldbe directly coupled to the single port, e.g. by using a Y-connector, thepower source equipment would detect a combined resistance of 12.5 kΩ andwould not provide power. (In the embodiment discussed above, powereddevices may change their internal resistance by switching to 50 kΩ inorder to achieve the combined resistance of 25 kΩ. In case of thisembodiment, however, an additional resistance of 25 kOhm may be includedin one of the lines of each cable forming the supply line, respectively.This additional resistance would thus be provided in series to theinternal resistance of the conventional powered devices, raising thetotal resistance in the respective parallel branches also to 50 kΩ, suchthat the combined resistance of the two conventional powered device andthe two devices for parallel powering would again be 25 kΩ. In otherwords, rather than switching between different resistances in thepowered devices as in the embodiment above, the present embodimentprovides for, for example, selectively adding further resistance to theresistance of the (conventional) powered device(s). Once the detectionis successful, the resistance may be removed again, as it wouldotherwise consume power.

It is to be noted that the aspects of the present invention as discussedabove with respect to the two embodiments may also be combined with eachother, even though such combination would complicate the processing forfinding the proper characteristic to be set/to be presented.

In a preferred embodiment, the controller and/or the characteristicsetting unit are arranged for changing the characteristic according to apredetermined scheme.

The predetermined scheme shared by the provided devices allows for asystematic trying of the available range of the characteristic and ifthe scheme is followed by the devices without temporal offset, thecorrect value may be found within one course of the scheme (unless, forexample, the number of (powered) devices exceeds a limit foreseen in thedetermination of the scheme).

It is to be noted that the predetermined scheme may allow for portionsof the scheme which may be determined by the device itself (see below),so that each device has its own combination of self-determined schemepart and predefined scheme part forming the predetermined scheme.

In a modification of the preferred embodiment, the predetermined schemeis a predetermined sequence of characteristics.

The predetermined sequence of characteristics may be that, in particularin case of an embodiment of claim 2, just a multiplier for the value ofstandard characteristic (e.g. a resistance of 25 kΩ) is increased foreach detected unsuccessful attempt of detection the powered devices,preferably until a maximum value is reached, e.g. 1, 2, 3, 4, . . . max.Nevertheless, the sequence may also follow an ordering based on otherconsiderations, like 1, 5, 3, 7, 6, . . . . The sequence may furthermoreinclude repetitions of multipliers (e.g. 1, 2, 3, 4, 2, 5, 6, 4, . . .).

In the situation of an embodiment according to claim 3, the abovesequences include also a multiplier of “0”, in order to address the casethat only a single (possibly conventional) powered device is connectedvia the device for parallel powering to the power source equipment.

Furthermore, in the situation of an embodiment according to claim 3, thesequence may also take into account that a device for allowing parallelpowering may be provided separately for each powered device (e.g. in theform of a cable connecting the powered device to a Y-connector or thelike, which, in turn, is plugged into a port of the power sourceequipment and may be provided for multiple powered devices together(e.g. such that a Y-connector or the like is provided by the device forallowing parallel powering (which might be plugged directly into a portof the power source equipment) and the multiple powered devices). Underthe assumption, for example, that the devices allowing for parallelpowering are by themselves only provided in parallel (and not inseries), while the characteristic were the resistance (with a resistanceof 25 kΩ being used for signaling the presence of a conventional powereddevice) a sequence may be provided by i·25 kΩ−25 kΩ/j, with i indicatingthe number of parallel branches and j indicating the number of powereddevices in the same branch as the present device for allowing parallelpowering.

Furthermore, it is not necessarily the case that the characteristic hasto remain constant between the detection attempts and it may also be thecase that the characteristic may be increased and/or decreased (quasi)continuous, so that the characteristic follows a continuous function oftime (or even a continuously differentiable function).

It is also foreseen that the predetermined scheme may be formed in partby a (predetermined) sequence (i.e. a series of discrete values) and inpart by a (quasi) continuous change of the characteristic value.

In a further modification of the preferred embodiment, the predeterminedscheme includes at least one characteristic based on information onprevious couplings between the powered device and the power sourceequipment.

As mentioned above, the scheme may include a portion or at least onevalue which would not be predefined by its value but only by itscharacter. In case the device is or becomes aware of the number of(other powered) devices connected in parallel, the correspondingcharacteristic may be used after a disconnection or the like caused bythe PSE and accordingly, and, if no change to the number of parallelpowered devices occurred, following detection process will quickly bebrought to a successful coupling. Another (possibly additional) optionmight be to use an average over a number of previous couplings. Afurther beneficial option (which might also be combined with the otheroptions) includes using as a first characteristic a value correspondingto the previously detected or learned number of parallel devices (or theaverage over a number of previous couplings) followed by a secondattempt (if necessary) using a characteristic corresponding to a numberof devices reduced by one, further followed (if necessary) using acharacteristic corresponding to a number of device increased by one.Using such option results, for example in the case of a broken orremoved parallel device, in a successful detection upon the second tryand, for example in the case of an added device, in a successfuldetection upon the third try (of course, the order may also be reversedor otherwise changed). A combination of these options might correspondto a situation dependent sequence of characteristic values correspondingto “previous number of devices”, “average of devices over previous ‘n’couplings”, “previous number of devices−1”, “previous number ofdevices+1”, followed by a predefined sequence as discussed above. It isto be noted that the characteristic based on information on previouscouplings needs not to be identical to a previously presentedcharacteristic but may also be just derived from the information.

In a yet further modification of the preferred embodiment, thecontroller and/or the characteristic setting unit are arranged forresetting the predetermined scheme upon a predetermined amount of changeof the presented characteristic and/or after lapse of a predeterminedperiod of time.

If, for example, two devices follow the same sequence but are out ofsynchronization, it may well be that the correct combined characteristicis newer achieved. Thus, based on a length of a sequence, a number ofrepetitions of such sequence or scheme, or on a duration of the process,the scheme may be restarted, preferably in such a manner that theresetting or restarting brings the connected device intosynchronization.

In another modification of the preferred embodiment, the device isarranged for outputting a reset signal for causing devices connected inparallel to the supply line to reset the predetermined scheme, and/orthe controller and/or the characteristic setting unit are arranged forresetting the predetermined scheme upon receipt of a reset signal.

In case any one of the devices connected to the supply line has foundthat the current attempt of connecting the powered device(s) to thepower source equipment might not succeed at all or for any other reason,the signal may be issued causing the compliant devices to restart theirprocessing, so that the connected devices may be become synchronized.

In another preferred embodiment the controller is arranged forcontrolling the characteristic setting unit to change the characteristicto a predetermined characteristic for indicating a particular situation.

Such situation may include the detection of an error (like wrong wiringor the presence of non-PoE loads (in case of powering according to PoE)on the supply line), where the characteristic may be changed to a valueconsistently preventing a detection of a combined load of the detectioncharacteristic. For example, in the case of powered devices bythemselves arranged for being powered parallel (see above), theresistance may be changed to a very low value (including an electricalshort), so that at least the PSE may be made aware of such error.

Additionally, the characteristic may be changed to reflect anunconnected state (e.g. substantially infinite resistance), so thispowered device would no longer influence the detection and connectionprocess of other similar powered devices connected to the supply line.

In case the characteristic is set, for example, by including a (further)impedance into the supply line, such impedance may be provided so highthat at also no coupling may occur.

In a further preferred embodiment, the controller is arranged, uponcoupling with the power source equipment, for determining a number ofpowered devices connected in parallel to the supply line from the setcharacteristic.

The knowledge about the total number of powered devices connected inparallel may be derived from the set characteristic in the case of asuccessful coupling by comparison to the detection characteristicprescribed by, for example, the PoE standard and used for, for example,the negotiation process for powered to be consumed by the powereddevice. Alternatively or additionally, the determined total number maybe made available to a different entity (including the case that thenumber is indicated to the user, e.g. in a display or by other means).

In a yet further preferred embodiment, the powered device comprises afirst connector for an incoming portion of the supply line and a secondconnector for an outgoing portion of the supply line.

A chain arrangement may conveniently achieved by providing an incomingand an outgoing connection so no additional equipment would be needed.

Nevertheless, the parallel connection may also be implemented by usingadditional parallel connectors branching, for example, an Ethernetcable, into one branch for the next powered device and one branch forthe further devices downstream.

In a preferred embodiment of the present invention, the powered deviceis arranged to be powered by Power-over-Ethernet, wherein furthermorethe characteristic is an impedance.

Power-over-Ethernet is a widespread standard for providing power and asthe characteristic for determining compliance with PoE impedance (andspecifically resistance) is commonly used.

In a further embodiment of the present invention, after initialcouplings between multiple powered devices and the power sourceequipment, the initial couplings are cancelled and repetitions of thesteps of the method as defined in claim 12 are provided in parallel, sofinal couplings are achieved together.

Under the assumption, in the context of Power-over-Ethernet and thecharacteristic being specifically the resistance, of a simple sequencelike 1, 2, 3, 4 and three devices on the supply line, a case may happenin which the third device is connected later and there is an offsetbetween the sequences by two detections. The first two devices mightshow a resistance of 100 kΩ each, the third one of 50 kΩ, resulting inthe combined value of 25 kΩ. The detection would then be successful,even though the PDs and the PSE might assume a wrong number of connecteddevices based on the respective sequences. In case the presumablydetected or determined number of parallel devices is of no furtherconsequence, the above described “hot-plugging” situation is of noconcern. If, however, there is a desire for deriving also—withoutadditional communication or the like—the number of devices connected inparallel to the supply line, after a successful coupling, such couplingmay be cancelled and all device involved will reset and restart theirchanging of the characteristic in a synchronized manner, then allowingfor a determination based on, for example, the course of the usedsequence.

In another aspect of the present invention a power source equipmentarranged for being coupled to one or more devices for allowing parallelpowering according to the invention via a supply line is presented,comprising a counting unit for counting a number of unsuccessfulattempts for coupling between the power source equipment and one or morepowered devices, and a determination unit for determining a number ofpowered devices connected in parallel to the supply line and coupled tothe power source equipment, in case of successful coupling between thepower source equipment and the one or more powered devices, based on thecounted number, wherein the power source equipment is arranged fortaking into account the determined number in providing power to the oneor more powered devices.

In a further aspect of the present invention a computer program orsoftware product is presented for controlling a device for allowingparallel powering, the software product comprising program code meansfor causing the powered device according to the invention to carry outthe steps of the method according to the invention when the softwareproduct is run on the powered device.

In a yet further aspect of the present invention a computer program orsoftware product is presented for controlling the provision of powerfrom a power source equipment to one or more powered devices via asupply line, the software product comprising code means for causing apower source equipment to carry out the steps of counting a number ofunsuccessful attempts for coupling between the power source equipmentand the one or more powered devices, determining a number of powereddevices connected in parallel to the supply line and coupled to thepower source equipment, in case of successful coupling between the powersource equipment and the one or more powered devices, based on thecounted number, and taking into account the determined number inproviding power to the one or more powered devices, when the softwareproduct is run on the power source equipment.

It shall be understood that the powered device of claim 1, the powersource equipment of claim 11, the method of claim 12, and the computerprograms of claims 14 and 15 have similar and/or identical preferredembodiments, in particular, as defined in the dependent claims.

It shall be understood that a preferred embodiment of the invention canalso be any combination of the dependent claims or above embodimentswith the respective independent claim.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following drawings:

FIG. 1 shows a conventional PoE lighting system with a star likecabling,

FIG. 2 shows a PoE lighting system including embodiments of theinvention,

FIG. 3 shows a powered device in accordance with an embodiment of theinvention,

FIG. 4 shows powered devices in accordance with another embodiment ofthe invention,

FIG. 5 shows an arrangement including a power source equipment, multipleconventional PoE powered devices and multiple devices for allowingparallel powering according to a further embodiment of the invention and

FIG. 6 shows a flow chart illustrating a method of controlling a powereddevice in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 2 shows a PoE lighting system including embodiments of theinvention.

The Power-over-Ethernet lighting system shown in FIG. 2 includes,similar to the conventional PoE lighting system shown in FIG. 1, a powersource equipment (PSE) 1 provided with a mains connection 4 (even thoughother means for powering the PSE may be used as well) and an Ethernetconnection 5 (which is optional). The present invention allows for usinga conventional PSE with the powered device(s) according to the presentinvention.

In contrast to the situation shown in FIG. 1, the powered devices (PD)10, 11 are not connected to the PSE 1 in a star-like way (i.e. each PDconnected by a dedicated line 3 to the PSE 1), but in two chains, usingEthernet cables 3 each. One set of PDs 11 is connected by means of aparallel connector 12, which branches the supply line. Further, theother set of PDs 10 is connected such that each PD 10 includes twosockets where the supply line is continued at the other socket.

In addition, in FIG. 2 also light sensors 13 are also connected, whilethese sensors 13 work in the usual manner.

As it can be seen from FIG. 2, in particular in comparison to FIG. 1,the required cable connections allow building chains where e.g. thesensors get wired to a chain with the related luminaires. The number ofloads per PSE output information can be used for the selection ofsuitable power levels.

FIG. 3 shows a powered device in accordance with an embodiment of theinvention.

The powered device (PD) shown in FIG. 3 comprises a first PoE port(incoming supply line), a data transceiver 20, a rectification unit 21,a control unit including resistance signaling means 22 (i.e. a circuitryfor selectively presenting a resistance to a detection by the PSE as anexample for an interface for presenting impedance) for signalingresistances to the PSE and a controller 23 including circuitry forcontrolling the resistance signaling means 22 for signaling resistancesto the PSE (also functioning as sensor for recognizing detectionattempts by a PSE), a PoE-controller 25, handling the classification andthe power flow towards the load and the load for consuming power (e.g. alight source, a sensor, a data gateway, a user interface, . . . ).

The data transceiver 20 is inductively coupled to the wires of theinternal lines connected to the supply line, which are provided to therectification unit 21. Beyond the rectification unit 21 the circuitry ofthe resistance signaling means 22 is provided, which is coupled to thecontroller 23. The PoE-controller is provided between the lines and theload 25.

The resistance signaling means is just an example of a setup designedfor presenting desired impedance. In particular, the invention is notlimited to the shown “R-stepping unit” and any functionality does nothave to be based on switches and resistors. Other means, if theimpedance is changed by adjusting the resistance, such as a controlledcurrent sink can be used, too.

The data transceiver 20 is optional to the invention and only needed incase full data communication is desired.

The rectification unit 21 is optional to the invention, in case fullflexibility on the input polarity is needed. When using the invention ina system with defined polarity and/or used pairs, a simpler or even norectification unit can be sufficient, too.

The PoE-controller 24 is optional to the invention. Classification canalso be handled, for example, by further set points in the resistancesignaling means 22, while power flow can also be controlled by the load25 itself.

It is to be noted that the load 25 does not necessarily have to beinternal to the powered device 11, as the powered device according tothe present invention may also provide power to a different entity.

FIG. 4 shows powered devices in accordance with another embodiment ofthe invention.

Two powered devices (PD) 10, connected to the PSE (not shown) are shownin FIG. 4. These PDs 10 differs from the first embodiment shown in FIG.3 in that they have two ports, enabling to daisy chain them withoutspecial cabling.

Each PD 10 comprises, a first PoE port, a second PoE port, circuitry forforwarding power from the first to the second port, a T-Switch 26 ordata hub for data communication, a rectification unit 21, a control unitincluding resistance signaling means 22 (i.e. a circuitry forselectively presenting a resistance to a detection by the PSE) forsignaling resistances to the PSE and a controller 23 including circuitryfor controlling the resistance signaling means 22 for signalingresistances to the PSE (just as in the embodiment of FIG. 3), aPoE-controller 25, handling the classification and the power flowtowards the load and the load for consuming power.

The key difference between the powered device 10 of the presentembodiment in comparison to that of the embodiment shown in FIG. 3 isthat the PD 10 has a second port such that other powered devices candirectly be connected to the PD 10. This is especially useful forconnection of an extension module (for increasing the light output orfunctionality) to the first PD in the line.

The comments provided above with respect to the rectification unit 21,the PoE-controller 24 and the load 25 apply also here. Similar to thedata transceiver, the T switch or data hub 26 is optional, for the casefull data communication is needed.

FIG. 5 shows an arrangement including a power source equipment, multipleconventional PoE powered devices and multiple devices for allowingparallel powering according to a further embodiment of the invention.

As shown in FIG. 5, two devices 30 for allowing parallel powering arecoupled via a T-Branch 12 to the same port of a power source equipment1. Two conventional powered devices 2 are coupled to one of the twodevices 30, while two further conventional powered devices 2 are coupledto the other one of the two devices 30.

The conventional powered devices 2 have an internal resistance of 25 kΩin accordance with the Power-over-Ethernet standard and the power sourceequipment 1 checks for such resistance to be connected to its ports,also in accordance with PoE.

The devices 30 are, in this exemplary embodiment, provided forconnecting in total up to 4 powered devices 2 in parallel to the port ofthe power source equipment and accordingly the characteristic settingunit 31 has four different settings, corresponding to the cases thateither one or two branches (devices for parallel powering) are providedin parallel and the cases that one or two powered devices are connectedto the device for parallel powering. In accordance with the formula i·25kΩ-25 kΩ/j discussed above, the respective resistance values are 0 Ω,12.5 kΩ, 25 kΩ and 37.5 kΩ, wherein these resistances are provided bythe characteristic setting unit 31 in one of the wires of the supplyline.

The devices 30 each are provided with a sensor 32 and a controller 33,wherein the sensor 32 is arranged for alerting the controller 33 aboutan application of a detection voltage and/or a detection current by thepower source equipment 1. In case the detection is unsuccessful, thecontroller 33 instructs the characteristic setting unit 31 to change tothe next characteristic, wherein these steps are repeating untileventually the detection is successful. In the illustrated case, thepower source equipment 1 detects a combined resistance of 25 kΩ in casethe characteristic setting units 31 each provide a resistance of 37.5 kΩin addition to the resistance already provided by the powered devices.

It is to be noted that the invention is not limited to cases where thenumber of powered devices coupled to different devices for allowingparallel powering is the same, even such cases have the benefit that alldevices for allowing parallel powering may use the same sequence andwill eventually arrive at a common proper setting for the characteristicvalue.

FIG. 6 shows a flow chart illustrating a method of controlling a powereddevice in accordance with an embodiment of the invention.

During detection, a certain voltage is applied by the PSE between somepairs of the Ethernet cable. A suitable load (being capable and designedfor receiving power via the Ethernet port) can load this voltage with aresistance of 25 kΩ. The PSE detects this load and continues with theclassification and powering sequence. If a resistance significantlydifferent from 25 kΩ is detected, the PSE assumes a load not compatiblewith PoE on that port, does not continue with the classification andpowering sequence and may poll again after some time. This procedure isdesigned such that loads not compatible with PoE are not exposed toharmful voltages and that a PoE-compatible load is detected, even ifthey are connected to the PSE during operation (hot plug).

The following discussion focuses on multiples of a standard resistanceof 25 kΩ as examples of the changed impedance, wherein it is to beunderstood that the tolerances provided by the standard also apply here.

The process illustrated in FIG. 6 starts with the powered device (seeabove) in an off or standby state (starting step 51). After “waking up”,first the multiplier n is first reset (resetting step 52). The PSEstarts a detection of connected powered device in detection step 53, sothat the powered device receives the detection voltage (reception step54). The controller of the powered device with set (or change) theinterface for presenting impedance (or resistance in this case) to avalue of the standard value (basically 25 kΩ) multiplied by themultiplier n.

Typically, the first value of n to be set (i.e. the initial value) willbe “1”, so that the powered device initially appears like a conventionalpowered device with a resistance of 25 kΩ(presentation step 55).

If the presented resulting or combined resistance is correct, the PSEcontinues with the classification (continuation step 56) and eitherfurther set point on the interface or the features of the PoE-controllercan be used for classification. After that, the PSE will, after theclassification and negotiation procedure (classification and negotiationstep 58) supply the full voltage (up to 56 V) to the PD, which can beforwarded to the load in operation step 59, eventually leading back tothe starting step 51 (e.g. after power down).

At some point after the classification, the powered device may confirmfrom the setting of “n” the number of parallel devices connected to thesupply line (confirmation step 57), which information may be used forpower negotiation.

In the case where the PD is the only PD connected to that channel of thePSE, the process as viewed from the PSE corresponds to the conventionalsituation and in such case to the outside the special features of theinvention appear not to be utilized.

In case the presented resulting or combined resistance is found not tobe correct by the PSE, the process follows a different branch of theflow chart.

Assuming the situation of two powered device connected in parallel, inthe presentation step 55, again each PD may signal simply 25 kΩ (n=1) tothe PSE. Having these two resistances in parallel, the total resistancewill be 12.5 kΩ, which differs significantly from the expected value;hence the PSE will terminate this cycle and try again later (terminationstep 60). In the following recognition step 61, the powered devicesnotice the fact that an (first) unsuccessful detection cycle hashappened (at a resistor setting of, in this case, 25 kΩ) and store this.Thereafter, in changing step 62, the multiplier n is changed to a newvalue (not necessarily just incremented by 1), followed by a handlingstep 62 for handling possible timeouts, errors or reset situations,after which the process returns to the detection step 53 (by the PSE).

Upon the next detection cycle, both PDs do each apply a resistance of 50kΩ to the input port. With two PDs in parallel, this will result in atotal of 25 kΩ, signaling a suitable load to the PSE, which will thencontinue with the classification procedure (step 56).

In case three PDs are connected in parallel, also the second cycle willnot result in 25 kΩ, hence it will be terminated (following the line ofsteps 60, 61, 62, 53), the information is again stored in the PD, whichwill then switch to the next multiplier value and will represent 3*25kΩ=75 kΩ each during the third detection process.

The process of applying a first multiple of 25 kΩ, a detecting anunsuccessful detection cycle, changing the multiple and applying thesecond multiple of 25 kΩ will be repeated until a maximum multiple(corresponding to the maximum number of allowed PDs in parallel) hasbeen applied. If this is reached, the PD will reset the sequence, switchto another sequence, initiate a pause time, or take similar actions.

Once a PD has detected or been informed about non-PoE-compatible loadson the same bus, it can signal this to the PSE, e.g. by choosing a lowresistance value during the next detection cycle, such that the 25 kΩcannot be reached, regardless of the setting in any of the parallel PDson the same bus.

In case to end the power delivery directly, the PD can overload the PSE,forcing a disconnect and apply the low resistance during the next andany following detection cycles, until the erroneous situation has beenresolved.

A problem that can occur is that of multiple PDs being unsynchronized.This can happen if part of the daisy chain is plugged in during thedetection phase of PDs that are already plugged in. Unless addressed,such situation may cause the PDs never to reach a combined 25 kΩdetection signature.

A solution to this is the following:

A maximum number of detection tries is defined (or a maximum timeperiod).

If a PD reaches this maximum it will connect a low impedance over thePoE lines.

Other PDs may notice that the detection mechanism stops for a certainamount of time and reset their state machine.

The PD that first reached the maximum will disconnect the low impedanceand also reset its own state machine.

Detection procedure resumes and now all connected devices are in thesame reset state and hence will proceed to detect successfully after arespective number of attempts.

The information on the steps (or multiplier) may also be an indicatorfor the number of devices in parallel on the bus. If, for example, themultiplier is just incremented by 1 for each try and the third detectioncycle is successful, each of the PDs knows that there are two othersimilar PDs in parallel. This is very valuable information and can beused for limiting the own power consumption, because all three loadswill have to share the total power budget of the PSE on that channel.

The information on the number of devices in parallel duringclassification can be captured and used by the PD, e.g. during theclassification procedure, where a lamp may signal its own power class inway, that other, parallel PDs can also signal their own power class.

Just like the PD, also the PSE can track (count) the unsuccessfuldetection tries and capture the same information, too. This informationcan be forwarded to a lighting management system, but also usedinternally, e.g. to account for a higher power budget at that port, orto apply different (no) error detection limits for the datacommunication on that channel

The PD according to the invention may be able to measure the impedancepresented by other devices on the supply line, e.g. by monitoring thevoltage/current at both PoE ports and directly jump to the impedancewhich will be needed. In case decoupling elements are present, this willallow every PD to understand its position in the chain and this mayfurther shorten the identification time.

The powered device of the present invention may itself be rather anactive parallel connector, a chain interface device shielding aconnected legacy PD from the negotiation cycles and handle these byitself until power gets granted and then present the available power tothe attached legacy PoE device which is not aware of the parallelingmechanism described herein.

In an embodiment of the invention, it is proposed to equip each nodewith a PD interface that can signal multiples of the standard definedunity load (25 kΩ with tolerances) during the detection process andincrease the load during a sequence of detection attempts. In that way,several nodes can share one PSE outlet and determine the number ofneighboring loads. At the same time, each node will offer fullfunctionality during “normal” stand-alone wiring. This powering conceptcan be combined with full or limited data communication capabilities.

In other words, the invention, in a preferred embodiment, foreseesequipping a node with a Powered Device (PD) controller that is capableof providing the correct impedance during detection towards the PSE,even if other loads are connected in parallel to the same output of aPSE.

From wiring point of view, each node may have two Ethernet sockets. Onesocket is acting as the input port and one as the output port, where itis also possible to reverse the assignment of input and output.Alternatively (i.e. for nodes which are only to be powered via PoE, butnot data communication via the normal Ethernet protocol is required),the functionality of delivering one PSE output to multiple PD inputs canbe solved by a special cabling or wiring method. Unlike classicalsplitters or Y-cables, which are normally used to split the 4 pairs ofone Ethernet port to two time 2 pairs, simple parallel connection of thetwo output port towards one input port can be performed, hence thiscould be seen as an Passive Parallel Connector (PPC, no T-Switch fordata) or an Active Parallel Connector (APC, with T-Switch for data).Further alternatively, special distribution means can be used, where thepassive power forwarding and the T-Switch for data is realized outsidethe PD. An example of such arrangement may be a particular Y-cabletogether with additional equipment which handles the features related tointerface, sensor and controller and forwards the data (if needed) andpower to a powered device connected downstream (which may even be aconventional powered device, if the additional equipment “isolates” theconventional powered device from the detection by the PSE. A particularbenefit of the invention lies in that the inventive circuitry takes carefor obeying the negotiation rules employed for PoE and at the same timecaptures information on the number of loads connected to that PSEoutlet.

One aspect of the present invention foresees a PD interface that iscapable of signaling multiples of the PoE unity load (25 kΩ) during adetection process, including an infinite resistance state. It may beprovided that the multiple is increased (1, 2, 3, 4, and so on) duringeach detection attempt, while any other sequence (e.g. 1, 5, 3, 7, 6, .. . ) can be used, too. Also, a (quasi-) continuous increase or decreasecan be applied as well. It is to be noted that tolerances (+/−x %) canbe applied to the nominal value of 25 kΩ, in particular as also PoEallows for such tolerances. The use of multiples of the unity load maybe limited while additionally also a no-load state may be provided (withinfinite resistance).

In preferred examples of the invention one or more of the following isprovided: information on the currently assigned multiplier value iscaptured, the sequence is restarted after detection of a resetcondition, a reset condition is signaled in a way, which is detectableto the other loads on the shared PSE output, an error (e.g. wrongwiring, presence of NON-PoE-Loads) is detected, the error is signaled tothe PSE

To some extent, features discussed in the present application may alsobe realized in the passive or active parallel connector PPC or APC,rather than in the powered device. As an example, the error detectionand handling of non-compatible loads may be realized there. For example,the impedance of the PD might be changed inside the PD, while thedetection of non-compliant loads and error handling is done externally,e.g. in the PPC and APC.

In its broadest terms, the powered device according to the presentinvention may be defined as a PoE powered device with adjustablebehavior during detection. Preferably, the behavior depends on thedetection history. Further, is may be the case that the detectionresistance can be changed, in particular as the resistance is increasedaccording to a predefined sequence. Indeed, the detection cycles untilidentification may be counted to yield the number of parallel PDs.

It is also foreseen that a PSE records identification impedances whennot successfully identifying PDs in order detecting the application ofthe present invention and count the number of PDs.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive; theinvention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality.

A single processor, device or other unit may fulfill the functions ofseveral items recited in the claims. The mere fact that certain measuresare recited in mutually different dependent claims does not indicatethat a combination of these measures cannot be used to advantage.

Operations like checking for the presence of the detection voltage ordetection current, and the control of the presented impedance can beimplemented as program code means of a computer program and/or asdedicated hardware.

A computer program may be stored and/or distributed on a suitablemedium, such as an optical storage medium or a solid-state medium,supplied together with or as part of other hardware, but may also bedistributed in other forms, such as via the Internet or other wired orwireless telecommunication systems.

Any reference signs in the claims should not be construed as limitingthe scope.

The invention claimed is:
 1. A device for allowing parallel powering,comprising: a characteristic setting unit for setting an impedance as acharacteristic, wherein the characteristic is used for signaling thepresence of a compliant powered device arranged to be powered byPower-over-Ethernet and wherein the characteristic is to be detected bya power source equipment via a supply line for powering, a sensorcoupled to the supply line, wherein the sensor is arranged for checkingfor an application of a detection voltage and/or detection current bythe power source equipment to the supply line for detection of acompliant device and for outputting a sensor signal when an unsuccessfulattempt for detection of a compliant device is recognized, and acontroller coupled to the characteristic setting unit and the sensorwherein the controller is arranged, upon receipt of the sensor signalfrom the sensor, for controlling the characteristic setting unit so tochange the characteristic wherein the device is a powered devicearranged for being powered via the supply line and the characteristicsetting unit is an interface for presenting the characteristic to thesupply line in order to signal the presence of the powered device orwherein the device is a connecting unit arranged for coupling the powersource equipment and at least one powered device and wherein the deviceincludes at least a portion of the supply line.
 2. The device accordingto claim 1, wherein the controller and/or the characteristic settingunit are arranged for changing the characteristic according to apredetermined scheme.
 3. The device according to claim 2, wherein thepredetermined scheme is a predetermined sequence of characteristics. 4.The device according to claim 2, wherein the predetermined schemeincludes at least one characteristic based on information on previouscouplings between the powered device and the power source equipment. 5.The device according to claim 2, wherein the controller and/or thecharacteristic setting unit are arranged for resetting the predeterminedscheme upon a predetermined amount of change of the presentedcharacteristic and/or after lapse of a predetermined period of time. 6.The device according to claim 2, wherein the device is arranged foroutputting a reset signal for causing devices connected to the supplyline to reset the predetermined scheme, and/or wherein the controllerand/or the characteristic setting unit are arranged for resetting thepredetermined scheme upon receipt of a reset signal.
 7. The deviceaccording to claim 1, wherein the device is a powered device arrangedfor being powered via the supply line and the characteristic settingunit in an interface for presenting the characteristic to the supplyline in order to signal the presence of the powered device, the devicefurther comprising a first connector for an incoming portion of thesupply line and a second connector for an outgoing portion of the supplyline.
 8. A power source equipment arranged for being coupled to one ormore devices according to claim 1 for parallel powering via a supplyline, comprising: a counting unit for counting a number of unsuccessfulattempts for coupling between the power source equipment and one or morepowered devices, and a determination unit for determining a number ofpowered devices connected in parallel to the supply line and coupled tothe power source equipment, in case of successful coupling between thepower source equipment and the one or more powered devices, based on thecounted number, wherein the power source equipment is arranged fortaking into account the determined number in providing power to the oneor more powered devices.
 9. A method for allowing parallel poweringmultiple powered devices according to claim 1 via a supply line, themethod comprising one or more repetitions of the steps of: setting animpedance as a characteristic used for signaling the presence of acompliant powered device arranged to be powered by Power-over-Ethernet,wherein the characteristic is to be detected by a power source equipmentvia the supply line, checking for an application of a detection voltageand/or detection current by the power source equipment to the supplyline and for outputting a sensor signal when an unsuccessful attempt fordetection of a compliant device is recognized, and causing a change ofthe setting of the characteristic in case the sensor signal is received.10. The method according to claim 9, wherein, after initial couplingsbetween multiple powered devices and the power source equipment, theinitial couplings are cancelled and repetitions are provided inparallel, so final couplings are achieved together.